Revert r223961 and r224074 (using IO message loop instead of DEFAULT).

ui/compositor/compositor.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 489 matching lines @@
       switches::kUIDisableThreadedCompositing);
 #else
   bool use_thread =
       CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kUIEnableThreadedCompositing) &&
       !CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kUIDisableThreadedCompositing);
 #endif
   if (use_thread) {
     g_compositor_thread = new base::Thread("Browser Compositor");
-#if defined(OS_POSIX)
-    // Workaround for crbug.com/293736
-    // On Posix, MessagePumpDefault uses system time, so delayed tasks (for
-    // compositor scheduling) work incorrectly across system time changes (e.g.
-    // tlsdate). So instead, use an IO loop, which uses libevent, that uses
-    // monotonic time (immune to these problems).
-    base::Thread::Options options;
-    options.message_loop_type = base::MessageLoop::TYPE_IO;
-    g_compositor_thread->StartWithOptions(options);
-#else
     g_compositor_thread->Start();
-#endif
   }
 
   DCHECK(!g_compositor_initialized) << "Compositor initialized twice.";
   g_compositor_initialized = true;
 }
 
 // static
 bool Compositor::WasInitializedWithThread() {
   DCHECK(g_compositor_initialized);
   return !!g_compositor_thread;
@@ skipping 260 matching lines @@
 }
 
 void Compositor::NotifyEnd() {
   last_ended_frame_++;
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingEnded(this));
 }
 
 }  // namespace ui